1. Field of the Invention
The present invention relates to a method of manufacturing a liquid crystal display device and, more particularly, to a method of manufacturing a color filter for a liquid crystal display device.
2. Description of the Related Art
In recent years, a liquid crystal display device has been widely utilized as a display for, e.g., a television or office automation equipment. This is because a liquid crystal display device has advantages of, e.g., low power consumption and light weight. In a liquid crystal display device having the above advantages, a demand has arisen for achieving larger size and high-quality color display. With this demand, a color filter for a liquid crystal display device is regarded as an important unit.
A conventional color filter for a liquid crystal display device has been manufactured by repeating the photolithography step. Since each pixel of the liquid crystal display device is extremely small, a high-precision color filter for the liquid crystal display device is required. In addition, the color filter must have excellent surface properties to form, e.g., an orientation film thereon. For this reason, high precision is required, and hence the manufacture by repeating the photolithography step results in poor productivity. In addition, the surface of the color filter must be flattened to form, e.g., an orientation film thereon. For this reason, cost of the liquid crystal display device is increased, and cost of an equipment including the liquid crystal display device is also extremely increased, as a matter of course.
In order to eliminate the above drawbacks, a printing method which can achieve the manufacture of a liquid crystal display device at lower cost than that of a dyeing method has been considered. In the printing method, a color filter or the like is manufactured by printing. However, foreign matters such as dust easily enter a color filter manufactured by the printing method. In addition, the surface of the color filter tends to be uneven due to the manufacturing method by printing. If the surface of the color filter is extremely uneven, it is difficult to form a transparent electrode or an orientation film on the color filter, thus easily degrading the display quality. For this reason, the conventional color filter manufactured by printing is impractical in spite of low cost.
In order to solve the above problems, a method is disclosed in Published Unexamined Japanese Patent Application No. 61-3123. According to this method, since the surface of a color portion formed by printing is polished and flattened, a color filter which does not adversely affect a transparent conductive film or the like can be manufactured. More specifically, the above application discloses a method of manufacturing a liquid crystal color display element, including the steps of printing and forming opaque portions on a substrate surface at predetermined intervals, printing color portions between the adjacent opaque portions, and polishing and flattening the color portions. According to this method, even if the surfaces of the color portions are uneven after the color portions are formed, the surfaces can be flattened by polishing, thus manufacturing a color filter suitable for a liquid crystal display device.
In order to improve contrast, however, a light-shielding portion in which a plurality of straight lines are arranged in a matrix form is formed in peripheral portions of pixels of the liquid crystal display device. When this light-shielding portion is micropatterned by the above printing method, printing ink easily spreads around the intersecting portions at which the straight lines cross each other at right angles because of the printing characteristics. For this reason, the light-shielding portion undesirably spreads to enter the light-transmitting portion, resulting in a defective liquid crystal display device. Therefore, a production yield of the liquid crystal display devices is degraded. As a result, in the conventional color filter for the liquid crystal display device, all the steps cannot be performed by the printing method, but a photolithography technique is employed.